1. Field of the Invention
The present invention relates to a lens drive device and a lens device, and more specifically to a lens drive device which is applied to a servo unit or the like detachably mounted to a TV lens body and functions as a drive portion for a focusing operation and a zooming operation of a lens system, and to a lens device which uses the drive device.
2. Description of Related Art
Currently, the speed of the zooming operation of a TV lens is required to be high for a quick shooting operation, and the lens moves from the telephoto end to the wide angle end (or from the wide angle end to the telephoto end) at a maximum speed of 0.6 sec. Therefore, to prevent a clank or the mechanical damage at the telephoto end or the wide-angle end, the speed-reduction control is performed for operating a brake before each stroke end. Since the force (of inertia, of friction, etc.) applied to the drive system depends on the TV lens model having each lens configuration and zooming mechanism structure, each model has its own optimum reduction characteristic (control method for realizing quick and smooth reduction).
However, since it is not clear in what type of TV lens the lens drive device referred to as a servo module detachably mounted to a lens body is mounted, the device is designed to have an average braking characteristic (with least common adjustments) in order to be used for each model.
In addition, in a servo module operating according to an analog signal, a general-purpose servo module has been conventionally used with analog (trimmer) adjustments, and the optimum braking characteristic has been assigned to a specific type of TV lens by trimmer adjustments. However, these adjustments are complicated, and further adjustments are required in a case where the servo module is re-mounted in another TV lens. Furthermore, it is difficult to restore the adjustments to initial values set at the delivery from the factory. Thus, the conventional servo module has lacked in generality.
On the other hand, the lens device disclosed by Japanese Patent Laid-Open No. 4-212941 includes means for detecting the type of movable lens, and is configured such that the brake operation position near the lens moving stroke end and the moving characteristic can be automatically set depending on the type of movable lens. However, to realize the automatic settings, it is necessary for the servo module side to receive necessary information from the lens body. Therefore, the technology cannot be used for the purposes other than the combination of the lens body and the servo module having the function of transmitting information. That is, it has the problem that an appropriate braking characteristic cannot be set in the case where the lens body itself is not provided with information providing means as in the aspect in which a servo module of digital type is applied to a lens body of analog type.